The present invention relates generally to implantable medical devices, and more specifically to such devices using high voltage flip chip components.
Currently, nearly all high voltage integrated circuit mounting is accomplished with wire bonding. Typical high voltage dice have active terminations on both sides of the die. Wire bonding involves attaching one end of a thin wire to a termination point on a side of a die, attaching the other end of the thin wire to a pad on a substrate, and encapsulating the die and connection points in an encapsulant to prevent damage to the wire bond. Wire bonding has numerous problems. Some of the problems are, for example, wire bonds are fragile and require multiple connections that may also make a structure more fragile.
A typical wire bonded high voltage die package 100 is shown in top view in FIG. 1A and in side elevation view on FIG. 1B. Die package 100 includes a substrate 102, a die 104 having a top side 106 and a bottom side 108. The die 104 is attached to the substrate 102 by two types of connections, an epoxy 110 connection and two wire bond connections 112. The epoxy 110 connection is between the substrate 102 and the back side 108 of the die 104. The wire bond connections 112 include a connection of a wire 116 between a pad 114 on the top side 106 of die 104 and a pad 118 on the substrate 102.
Because of fragility and problems with arcing and wire damage and because the wires necessarily stick up from the die as shown in FIG. 1, once the die 104 is wire bonded on the top side 106 and the substrate 102, and conductively epoxied to the substrate on the back side 108, the entire area of the wire bonding connections 112 and die 104 is encapsulated. The encapsulation covers the entire area of the die, in addition to the entire area of the wire bond contact to the substrate, plus the vertical height of the wire off the die. The encapsulant die size is quite large.
As implantable medical devices become smaller and smaller, and as more and more components are added to such devices, the real estate available for components is shrinking. Components too are shrinking in size, but the need for improving the use of available volume and real estate continues.
In implantable medical devices, the footprints of dice and stacked dice packages typically exceed the bottom die size. For example, when wire bonding is used to electrically connect a die to rigid or flexible interposers, the package size is much larger than the bottom die size, and is therefore substantially size inefficient.
In one embodiment, a method for assembling an implantable medical device includes assembling a substrate containing circuitry for use in a medical device, and mounting a flip chip high voltage die to the substrate.
In another embodiment, a method for reducing the size of an implantable medical device includes preparing a high voltage device with terminations on a single side of the device die for surface mount technology application. The process includes preferably mounting the high voltage die on a reduced size implantable medical device substrate, and assembling the substrate into a reduced size body.
In yet another embodiment, an implantable medical device includes a body, a substrate, and a high voltage die mounted to the substrate using flip chip components. The high voltage die in one embodiment is a die such as that disclosed herein.
Other embodiments are described and claimed.